On motion of the eccentricity vector for IRS-1A and 1B

Based on the differential equations for the perturbations in eccentricity e and perigee omega due to J2 and J3, an analytical solution is obtained for the time history of e and omega. The analytical solution is first validated with the numerical solution. Using the definitive orbital data of IRS-1A and IRS-1B for about 4.5 months, it is shown that the analytical solution fairly represents real-world data. The error function is observed to have a periodicity equal to the periodicity of the eccentricity vector itself.